3GPP 24.501 v20.0.0 — the document's own text
8.2.6.25 Mobile station classmark 2
Taught in 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).
This IE shall be included if the UE supports 5G-SRVCC from NG-RAN to UTRAN (see 3GPP TS 23.216 [6A]).